As the conventional chlorination process for imparting gloss to wool fibers, there has been tried a method wool fibers are treated in a concentrated aqueous solution of sodium chloride by a mixed acid aqueous solution of a chlorinating agent. In this method, the chlorination is very vigorous, and not only cuticular cells protecting the interiors of wool fibers but also cortical cells are indiscriminately destroyed and the wool fibers are hardened and roughened. Moreover, the mechanical properties are degraded in certain portions and when these fibers are dyed, uneven dyeing is caused because of the difference of the absorbing capacity and the dyed product comes to have a patched appearance. Still further, the fastness is drastically degraded. In short, only damaged fibers are obtained by the above-mentioned conventional chlorination method.
According to the present invention, a necessary amount of an acid is included in the inside of projection scaly edge portions of wool fibers where water is absorbed very uniformly, while other portions are controlled by a saturated solution of a neutral salt so that the acid is not allowed to permeate in these portions, and then, in a chlorinating bath, chlorine is activated by the included acid and chlorination is accomplished only in the limited portions precisely. Therefore, the chlorination method in which all the defects of the conventional method are eliminated is established according to the present invention. At the subsequent reducing and water-washing steps, the surfaces of wool fibers are smoothened. Thus, according to the present invention, wool fibers are modified and the quality grade thereof is advanced by the specific method.
The fact that the endo cuticle of the edge portion has a structure capable of easily adsorbing or absorbing water therein though the surface of the wool fiber is water-repellent is disclosed in the following reference:
"Structure of Surface Layer of Wool" compiled by Ryoji Nakamura, in "Crimp, Wool and Technique", No. 33, pages 3 to 9, published on June 30, 1976 by the International Wool Secretary.